DNA vaccination is a novel approach to immunization and offers new hope for the development of a vaccine against human immunodeficiency virus-1 (HIV-1). HIV-1 DNA vaccines use direct inoculation of DNA plasmids to express HIV-1 antigens in vivo and to raise immune responses. We propose studies focusing on the immunogenicity of HIV-1 DNA vaccines. Preliminary studies with DNA vaccines expressing envelope (Env) protein of HIV-1 in vivo demonstrated that different forms of Env (gp120, gp140 or full- length gp160) had different levels of immunogenicity as determined by their ability to raise anti-Env antibody responses. The full-length Env was the least immunogenic. New strategies aimed at raising high neutralizing antibody responses against this form of Env will provide fundamental information useful for the ultimate development of effective HIV-1 vaccines. With the ability to express antigens in vivo and to preserve their native conformation, DNA vaccination is an ideal candidate for this task. We propose to study the immunological mechanisms which determine the types and levels of anti-Env antibody responses by using newly improved and existing HIV-1 DNA vaccines. The isotype and affinity profile of serum antibody responses will be measured. The trafficking of Env-specific, antibody forming cells will be analyzed. The levels of specific cytokine-secreting cells will be assayed following immunizations to determine the nature of the elicited immune responses. More importantly, we propose to test the roles of cytokines and adjuvants on Env-specific antibody responses. Finally, co-inoculation of DNA plasmids which express highly immunogenic, non-HIV proteins will be studied to see if they can provide additional T-helper functions to enhance HIV-1 Env- specific antibody responses. The information generated from these studies will not only help us develop a viable DNA vaccine against AIDS but also provide valuable information regarding the critical interactions between HIV-1 and the immune system.